From reading Darwin's Autobiography I met a man I wasn't really expecting (well to be honest I'm not really sure what I was expecting in the first place). Darwin came across quite a humble man who seemed to be quite fair in what he said. He talked about some funny antidotes that happened to him while he was young, we see a man that he loved to go shooting and for long walks (and discussions) with people. His father even considered Darwin to join the church, which Darwin reminisces at the time he believed the creeds to be true and says "I had scruples about declaring my belief in all the dogmas of the Church of England; though otherwise I liked the thought of being a country clergyman." (not included in this reprint)
Darwin attributes one of his main influences to a man called Professor Henslow, who was a strong Anglican. Henslow gets a really good write up by Darwin and he seemed to live the Christian life well.
I have not as yet mentioned a circumstance which influenced my whole career more than any other. This was my friendship with Professor Henslow... He kept open house once every week when all undergraduates and some older members of the University, who were attached to science, used to meet in the evening.
Never in my life have I seen such wrath painted on a man's face as was shown by Henslow at this horrid scene [a mob attacking two men]. He tried repeatedly to penetrate the mob; but it was simply impossible. He then rushed away to the mayor, telling me not to follow him, but to get more policemen.
Henslow's benevolence was unbounded, as he proved by his many excellent schemes for his poor parishioners, when in after years he held the living of Hitcham. (All these quotes not included in this reprint)
Christians should take note and wonder how non-believers will remember them and their actions.
In the chapter provided, Darwin talks about the reasons, and not feelings, that have lead him to be agnostic about God. One of the arguments Darwin mentions is all the suffering in the world
This very old argument from the existence of suffering against the existence of an intelligent First Cause seems to me a strong one; whereas, as just remarked, the presence of much suffering agrees well with the view that all organic beings have been developed through variation and natural selection (page 95)
even though earlier he also declares that:
According to my judgment happiness decidedly prevails, though this would be very difficult to prove. If the truth of this conclusion be granted, it harmonizes well with the effects which we might expect from natural selection. (page 94)
Which sounds a little like a feeling to me...
Darwin reflects that while in a large Brazilian forest he was ecstatic, his breath was taken away and something inside him made his think that man is more than just an animal. He later says "But now the grandest scenes would not cause any such convictions and feelings to rise in my mind. It may be truly said that I am like a man who has become colour-blind, and the universal belief by men of the existence of redness makes my present loss of perception of not the least value as evidence." (page 96) He once had joy in the feeling of the infinite, but now wouldn't feel it, and laments it as someone who now can not see in colour. Thats kinda of a big loss...
The end of the short chapter concludes:
When thus reflecting I feel compelled to look to a First Cause having an intelligent mind in some degree analogous to that of man; and I deserve to be called a Theist. This conclusion was strong in my mind about the time, as far as I can remember, when I wrote the 'Origin of Species;' and it is since that time that it has very gradually, with many fluctuations, become weaker. But then arises the doubt, can the mind of man, which has, as I fully believe, been developed from a mind as low as that possessed by the lowest animals, be trusted when it draws such grand conclusions?
I cannot pretend to throw the least light on such abstruse problems. The mystery of the beginning of all things is insoluble by us; and I for one must be content to remain an Agnostic. (page 96)
Darwin touches on the argument from reason. If our minds have evolved over time, how do we know it is accurate, and not just random biological movements telling us things. This argument could also flow to the assumption about natural selection and eveything else we know.
My understanding of terms is that a theist believes there is a deity, an atheist believes there is no deity, and an agnostic doesn't know. Darwin declares himself to be an agnostic, which leaves me wondering why (like some other authors) he was included in this book for Atheists.
You can read Darwin's Autobiography here (along with other letters he wrote) Volumn 1 has this religion chapter. This version I think is formatted better, but it doesn't have his chapter on religion.